The present invention relates to a method for supplying fresh auxiliary material, which is added to a stream of crude gas laden with wet paint overspray before the stream of crude gas passes through at least one filter element for separating the overspray from the stream of crude gas, to at least one filter device which comprises at least one receptacle for auxiliary material, which is in an operating position, while the stream of crude gas is passing through the filter element.
Such a method is known, for example, from DE 10 2005 048 579 A1.
With this known method, the dry separation of the wet paint overspray from the stream of crude gas of a spray booth takes place in the filter device once fresh, flowable, particulate auxiliary material designated as “precoat” material has been released into the stream of crude gas with a nozzle arrangement.
This auxiliary material serves the purpose of being deposited on the surfaces of the filter element as a barrier layer in order to prevent these surfaces from becoming clogged due to overspray particles adhering thereto. As a result of periodic cleaning of the filter elements of the filter device, the mixture consisting of auxiliary material and wet paint overspray passes from the filter elements into receptacles for auxiliary material, from which it can be withdrawn by suction in order to be supplied to the nozzle arrangement for renewed use as auxiliary material. Furthermore, the mixture consisting of auxiliary material and wet paint overspray which is present in the receptacle for auxiliary material can be whirled up by means of pulses of compressed air from a compressed air lance in order to rise up out of the receptacle for auxiliary material to the filter elements and be deposited on them.
In order to prevent auxiliary material passing into the application area of the paint plant while auxiliary material is being supplied to the stream of crude gas from the nozzle arrangement, the flow path of the stream of crude gas from the application area to the filter device is closed periodically in this known method. The auxiliary material which has been whirled up from the receptacles for auxiliary material is not sufficient to generate an adequate protection layer on the filter elements. In addition, fresh auxiliary material can be introduced into the stream of crude gas only through the nozzle arrangement.
The object underlying the present invention is to provide a method of the type specified at the outset which enables better action of the auxiliary material on the stream of crude gas and makes a particularly efficient supply of fresh auxiliary material to the at least one filter device possible.